US9608723B2ActiveUtilityPatentIndex 73
Carrier-signal power ratio control in direct detection optical systems
Est. expiryOct 20, 2034(~8.3 yrs left)· nominal 20-yr term from priority
H04J 14/0227H04B 10/0799H04B 10/572H04B 10/07955H04B 10/548
73
PatentIndex Score
3
Cited by
10
References
28
Claims
Abstract
System and method embodiments are provided for carrier-signal power ratio (CSPR) control in direct detection optical systems. In an embodiment, a method for CSPR control in a direct detection optical system includes receiving an electrical signal in a receiver (RX) digital signal processor (DSP), wherein the electrical signal is obtained from a corresponding optical signal via a direct detection component; estimating, a CSPR for the electrical signal; generating one of a control signal according to the CSPR; and transmitting the control signal to one of an optical filter and a laser, wherein the wavelength control signal controls causes a center wavelength (CW) of one of the optical filter and the laser to be adjusted such that an offset between the CW of the laser and the CW of the optical filter results in a desired CSPR.
Claims
exact text as granted — not AI-modifiedWhat is claimed is:
1. A method for carrier-signal power ratio (CSPR) control in a direct detection optical system, comprising:
receiving an electrical signal in a receiver (RX) digital signal processor (DSP) wherein the electrical signal is obtained from a corresponding optical signal via a direct detection component;
estimating, with the RX DSP, a CSPR for the electrical signal, wherein the estimating the CSPR comprises estimating the CSPR in a digital domain according to digital samples in a quadrature amplitude modulation (QAM) demodulator;
generating, with the RX DSP, a control signal according to the CSPR; and
transmitting, with the RX DSP, the control signal to a first optical element, wherein the control signal causes a center wavelength (CW) of the first optical element to be adjusted such that an offset between the CW of the first optical element and the CW of a second optical element results in a specified CSPR.
2. The method of claim 1 , wherein the first optical element comprises one of an optical filter and a laser and wherein the second optical element comprises the other one of the optical filter and the laser.
3. The method of claim 1 , wherein data traffic through the system is uninterrupted.
4. The method of claim 1 , wherein estimating the CSPR comprises determining a ratio of signal power and a signal due to signal-signal beat interference (SSBI).
5. The method of claim 1 , wherein estimating the CSPR comprises determining an estimated CSPR, wherein the estimated CSPR comprises a CSPR′, and wherein the CSPR′ is determined according to:
CSPR
′
=
10
log
10
(
∑
n
=
N
1
N
2
ⅆ
n
2
2
∑
n
=
1
N
1
ⅆ
n
2
)
where, n is subcarrier index, dn is training data on an n-th subcarrier, N1 is a number of subcarrier in a gap, and N2 is a total number of subcarriers in gap and data sections.
6. The method of claim 1 , wherein estimating the CSPR comprises determining an estimated CSPR, wherein the estimated CSPR comprises a CSPR′, and wherein the CSPR′ is determined according to:
CSPR
′
=
1
N
avg
∑
N
avg
10
log
10
(
∑
n
=
N
1
N
2
ⅆ
^
n
2
2
∑
n
=
1
N
1
ⅆ
^
n
2
)
where N avg is a number of symbols under averaging, N1 is a number of subcarrier in a gap, N2 is a total number of subcarriers in gap and data sections, dn is training data on an n-th subcarrier, and {circumflex over (d)}n is data on an n-th subcarrier.
7. The method of claim 1 , wherein generating the control signal comprises averaging the estimated CSPR across multiple WDM channels and converting the average estimated CSPR into a single tuning voltage for a single-side band (SSB) filter.
8. The method of claim 7 , wherein the average CSPR is determined according to:
CSPR
avg
=
1
N
channel
∑
N
channel
CSPR
i
where CSPR avg is the average CSPR, N channel is the total number of channels, and CSPR i is an estimated CSPR for the i th channel.
9. The method of claim 1 , wherein estimating the CSPR comprises receiving, at a central office receiver, an estimated CSPR from a DSP in a client side transceiver via a feedback channel, wherein the DSP in the client side transceiver estimates the CSPR from a received signal received from the central office transmitter.
10. The method of claim 1 , wherein estimating the CSPR comprises estimating the CSPR of a signal received by a central office receiver from a client side transmitter and using the estimated CSPR of the signal received from the client to adjust the CSPR of the central office transmitter.
11. A network component configured for carrier-signal power ratio (CSPR) control in a direct detection optical system, the network component comprising:
a processor; and
a computer readable storage medium storing programming for execution by the processor, the programming including instructions to:
receive an electrical signal, wherein the electrical signal is obtained from a corresponding optical signal via a direct detection component;
estimate a CSPR for the electrical signal;
generate a control signal according to the CSPR; and
transmit the control signal to a first optical element, wherein the control signal causes a center wavelength (CW) of the first optical element to be adjusted such that an offset between the CW of the first optical element and the CW of a second optical element results in a specified CSPR,
wherein the instructions to estimate CSPR comprise instructions to estimate the CSPR in a digital domain according to digital samples in a quadrature amplitude modulation (QAM) demodulator.
12. The network component of claim 11 , wherein the first optical element comprises one of an optical filter and a laser and wherein the second optical element comprises the other one of the optical filter and the laser.
13. The network component of claim 11 , wherein data traffic through the system is uninterrupted.
14. The network component of claim 11 , wherein the instructions to estimate the CSPR comprise instructions to determine a ratio of signal power and a signal due to signal-signal beat interference (SSBI).
15. The network component of claim 11 , wherein the instructions to estimate CSPR comprise instructions to determine an estimated CSPR, wherein the estimated CSPR comprises a CSPR′, and wherein the CSPR′ is determined according to:
CSPR
′
=
10
log
10
(
∑
n
=
N
1
N
2
ⅆ
n
2
2
∑
n
=
1
N
1
ⅆ
n
2
)
where, n is subcarrier index, dn is training data on an n-th subcarrier, N1 is a number of subcarrier in a gap, and N2 is a total number of subcarriers in gap and data sections.
16. The network component of claim 11 , wherein the instructions to estimate CSPR comprise instructions to determine an estimated CSPR, wherein the estimated CSPR comprises a CSPR′, and wherein the CSPR′ is determined according to:
CSPR
′
=
1
N
avg
∑
N
avg
10
log
10
(
∑
n
=
N
1
N
2
ⅆ
^
n
2
2
∑
n
=
1
N
1
ⅆ
^
n
2
)
where N avg is a number of symbols under averaging, N1 is a number of subcarrier in a gap, N2 is a total number of subcarriers in gap and data sections, dn is training data on an n-th subcarrier, and {circumflex over (d)}n is data on an n-th subcarrier.
17. The network component of claim 11 , wherein the instructions to generate the control signal comprises instructions to average the estimated CSPR across multiple WDM channels and converting the average estimated CSPR into a single tuning voltage for a SSB filter.
18. The network component of claim 17 , wherein the average CSPR is determined according to:
CSPR
avg
=
1
N
channel
∑
N
channel
CSPR
i
where CSPR avg is the average CSPR, N channel is the total number of channels, and CSPR i is an estimated CSPR for the i th channel.
19. The network component of claim 11 , wherein the instructions to estimate the CSPR comprises instructions to receive, at a central office receiver, an estimated CSPR from a digital signal processor (DSP) in a client side transceiver via a feedback channel, wherein the DSP in the client side transceiver estimates the CSPR from a received signal received from the central office transmitter.
20. The network component of claim 11 , wherein the instructions to estimate the CSPR comprises instructions to estimate the CSPR of a signal received by a central office receiver from a client side transmitter and using the estimated CSPR of the signal received from the client to adjust the CSPR of the central office transmitter.
21. A direct detected optical transmission system, comprising:
a laser;
an optical filter in a signal path of an optical output from the laser; and
a controller communicably coupled to at least one of the laser and the optical filter, wherein the processor is configured to estimate a carrier-signal power ratio (CSPR) in the direct detected optical transmission system, wherein the processor is further configured to generate a control signal according to the CSPR, wherein the processor is further configured to send the control signal to one of the laser and the optical filter, and wherein the control signal causes a center wavelength (CW) of one of the optical filter and the laser to be adjusted such that an offset between the CW of the optical filter and the CW of the laser results in a specified CSPR in a transmitted optical signal,
wherein estimating the CSPR comprises estimating the CSPR in a digital domain according to digital samples in a quadrature amplitude modulation (QAM) demodulator.
22. The direct detected optical transmission system of claim 21 , wherein the transmitted optical signal comprises an Orthogonal Frequency-Division Multiplexing (OFDM) signal.
23. The direct detected optical transmission system of claim 21 , wherein the processor comprises a digital signal processor (DSP).
24. The direct detected optical transmission system of claim 21 , wherein data traffic through the direct detected optical transmission system is uninterrupted.
25. The direct detected optical transmission system of claim 21 , wherein estimating the CSPR comprises determining a ratio of signal power and a signal due to signal-signal beat interference (SSBI).
26. The direct detected optical transmission system of claim 21 , wherein generating the control signal comprises averaging the estimated CSPR across multiple Wavelength Division Multiplexing (WDM) channels and converting the average estimated CSPR into a single tuning voltage for a single-side band (SSB) filter.
27. The direct detected optical transmission system of claim 21 , wherein bi-directional links are substantially identical, and wherein the CSPR is estimated from a signal from a client side transmitter.
28. The direct detected optical transmission system of claim 21 , further comprises a receiver configured to receive an estimate of the CSPR from a client side component via a feedback channel, wherein the client component estimated the CSPR of a signal received from the laser.Cited by (0)
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